There is known a mass exchange contact device comprising a plate face with contact elements. The plate face includes ring-shaped holes with cross-pieces, which holes are disposed along the periphery of the contact elements. A central hole is disposed under the contact element, a branch pipe and a ring are mounted on the axe of central hole. The ring is equipped with a movable double-acting valve arranged in the middle thereof. The valve is made of plates with central holes, wherein the plates are connected by means of distance poles. The upper hole is used for passing the branch pipe. An interrupting valve is mounted on a rod situated between limiters of ascending and descending under the lower hole (USSR inventor certificate No. 1307643).
The disadvantages of the mentioned device are: it's composed of two movable parts; there is a restriction of the opening cross-section of branch pipe for passing gas (steam), as well as a restriction of the ringed holes' opening cross-section for a liquid flow. These disadvantages increase the plate's hydraulic resistance at the time of gas (steam) passing, and the time of transferring liquid from one plate to another.
A mass exchange contact device has been described in the U.S. parent application Ser. No. 12/225,575 filed by the instant inventors. The ‘parent’ mass exchange contact device includes an upper tray associated with a contact element, a casing, a movable double-acting valve, lifting and descending limiters. The casing has an upper row of orifices and a lower row of windows, the rows are situated along the casing's perimeter, and the movable valve is composed of two plates installed one above the other and connected by a distance rod. The parent device is equipped with an additional lower tray.
The contact element serves as a limiter for lifting the double-acting valve and the bottom edge of the casing serves as a limiter for descending the valve. The lower edges of the windows are made at the level of the lower tray. The contact element comprises a specific barbotage unit made in the form of an inner cap with tangently bent strips. The height of the windows is essentially equal to the height of the double-acting valve, and in the ending positions of the double-acting valve, the lower plate divides the opening of windows into equal sections.
The efficiency of the ‘parent’ device however can be increased by dividing the barbotage space into a number of layers thereby enlarging the mass-exchange surface, which is disclosed herein further.
For example, U.S. Pat. No. 5,523,062 teaches: “A distribution element is provided which may be used in packed columns to redistribute the gas and liquid flow evenly across the column. Most simply the element comprises a corrugated plate having openings only at the peaks and valleys of the corrugation. There are no openings in the sloped sides of the corrugations. The distribution element is spaced within the packing to most advantageously utilize the redistribution characteristics of the element for a given system.” The U.S. Pat. No. 5,523,062 is hereby entirely incorporated by reference.
Another U.S. Pat. No. 6,206,349 describes: “Fluid—fluid contacting apparatus is provided with a structured packing comprising a series of packing elements fabricated from sheets of crimped material in such a way that the corrugations in each sheet extend obliquely with respect to the direction of bulk fluid flow through the apparatus. Each packing element is oriented with the sheets thereof in a plane which is angularly displaced with respect to the sheets of neighboring elements. A mechanism is provided at or in the vicinity of the interface between neighboring elements for reducing the pressure drop imposed on the continuous phase as it passes from one element to the next.” The U.S. Pat. No. 6,206,349 is hereby entirely incorporated by reference.
Another U.S. Pat. No. 6,513,795 discloses “A layer of mixed-resistance structured packing includes: a first structured packing having a first packing resistance; and a second structured packing generally horizontally adjacent the first structured packing, the second structured packing having a second packing resistance different than the first packing resistance. The layer of mixed-resistance structured packing is used in exchange columns for exchanging heat and/or mass between a first phase and a second phase in processes such as cryogenic air separation. Use of the layer of mixed-resistance structured packing reduces HETP (height equivalent to a theoretical plate) in the exchange columns and processes. A method also is provided for assembling the layer of mixed-resistance structured packing in an exchange column.” The U.S. Pat. No. 6,513,795 is hereby entirely incorporated by reference.
A disadvantage of the above-mentioned devices is that the volatile phase changes its speed along the height of the column due to varying the share of the volatile phase. Therefore, the ascending volatile phase flow cannot stably support the liquid phase in a cyclic mode. This leads to the fact that the liquid phase falls down within the lower speed sections of the column, whereas the liquid phase is pushed out within the higher speed sections of the column. Hence, empty zones appear within the structured packing elements, the phases move unevenly, causing low separation efficiency. This prevents arranging an efficient mass-exchange process with separate movements (i.e. in a cyclic mode) of the phases in the column. This disadvantage is conditioned by the fact that the packing element creates a resistance to the liquid phase moving along the mass-exchange tray, and a mass-exchange surface is formed only due to barbotage.
The mentioned above devices have also another disadvantage of stochastic formation of the mass-exchange surface on the trays, while the liquid is intermingled throughout the whole volume of liquid phase.
Another U.S. Pat. No. 4,471,154 teaches: “A distillation-reactor for separating constituents of a feedstock having similar boiling points includes at least one stage with containing screens defining a series of containment volumes for a heterogeneous particulate catalyst. The catalyst is fluidized within the volumes defined by the containing screens by the action of vapor passing through the tray. Liquid flowing across the tray intimately contacts the fluidized catalyst and vapor without the occurrence of liquid back-up or high pressure drop.” U.S. Pat. No. 4,471,154 is hereby entirely incorporated by reference.
Yet, another U.S. Pat. No. 5,536,699 teaches: “The packing having catalytic or adsorbent agents, which is provided for at least one fluid medium, comprises packing elements (10) disposed in stacks, which are assembled from layers aligned along the main direction of flow (2). The layers are formed by packing parts (1), the walls (2) of which are permeable for the medium. The packing parts contain a catalyst material (3). Between the packing parts are provided flow ducts, which intersect and are open to one another. According to the invention the layers are formed by a plurality of packing parts (1), the packing elements (10) comprise support structures (4) into which the packing parts are inserted, and the packing parts are substantially cylindrical.” U.S. Pat. No. 5,536,699 is hereby entirely incorporated by reference.
A shortcoming of the devices described in the last two patents is that the amount of costly catalyst used is high, which makes the devices expensive. However, if one could increase the efficiency of dividing the components and enhance the uniformity of distribution of the catalyst, the required amount of catalyst would be reduced, making the device less expensive. The related art devices also cannot control the speed of chemical reactions, since they don't provide for regulation of the time of introduction of the volatile phase into the column.